I'd make sure the earphones aren't defective first. If not wiggle the audio connections.

Pinnovators can solve the second problem. I've bought a second through the door volume control for HOBBIT as well.

It might be the plug itself. The stereo mini jack on the end of your earphones has 3 lines separating right, left and ground. What you plug into (the female part) has 3 pieces of metal that correspond. You might have a left (or right) channel that's not aligned correctly or the connection is too weak. You might press on the WOZ side connections while the earphones are plugged in with a tooth pick.

Otherwise the sound board is located to the right just behind the coin box. There are wires going in and out. Wiggle the connections from the earphone jack to the board and if that doesn't work you might reseat any plugs to the board. If that doesn't work call Lloyd or Frank at JJP - they know what they're doing while I'm only guessing.

Try wiggling connections at back of big silver box this side of woofer. This should affect external speakers only but who knows.